Fluid Dynamic factors in reciprocating piston pump systems can cause several modes of mechanical failure of pump components. Failed components include fluid end modules, power end frames, cranks, connecting rods, bearings, gears, drive couplings and transmissions.
Pump component failures result from excessive mechanical cyclic stress from fluid dynamic factors or cavitation, or the combination of high tensile stress and corrosion. The effects of fluid corrosive properties are difficult to define but are important in the cyclic stress corrosion process. Inadequate pump maintenance leads to increased cyclic stress from changes in the pump fluid dynamics.
The general design of pump fluid-end modules with intersecting bores of the piston and valve chambers result in high stress concentrations that may result in the stress being as much as two to four times the normal hoop stress observed in pump cylinders. Generally the stress level must be past the material yield point to initiate and propagate a crack to ultimate failure such as the leaking of fluid from the pump fluid-end module.
Life cycle cost of pump components is generally evaluated either by pump operating cycles or hours of operation. In fixed speed and pressure applications such parameters are good approximations. However, using pump cycles or hours of operation will lead to inaccurate conclusions if pump speeds, system pressures or system dynamic factors, such as hydraulic resonance change during operation.